1. Field of the Invention
The present invention relates to a modular power plant and also to an aircraft provided with a lift rotor that is driven in rotation by the power plant.
2. Description of Related Art
A power plant of such an aircraft usually includes a turbine engine driving a main gearbox.
A turbine engine usually comprises a gas turbine possessing a gas generator that drives a working turbine in rotation. The working turbine may be a so-called “free” turbine that is independent of the gas generator. The gas generator generally has at least one compression stage feeding a combustion chamber with compressed air.
The main gearbox includes a rotor mast for driving the lift rotor in rotation. Furthermore, the main gearbox may include an outlet for driving a rotor that controls yaw movement of the aircraft, for example.
Connection means and angle drive takeoff means may then possibly be interposed between the working turbine and the main gearbox. For example, such connection means include members for accommodating angular misalignments between two rotating shafts.
A turbine engine is generally arranged horizontally on a support platform. In other words, an outlet shaft from a turbine engine is in a horizontal position. Conversely, the support platform carries the main gearbox in a position that is substantially vertical, the rotor mast that is rotated by the main gearbox being substantially vertical.
Old generation turbine engines generally present considerable weight and size that can make them difficult to install. More particularly, such old generation turbine engines may present relatively high fuel consumption.
Certain modern turbine engines are nevertheless relatively compact. Turbine engines are known that comprise a single compression stage and a combustion chamber that is said to be “inverted” and that enables the overall size of the turbine engine to be greatly reduced. For convenience and in order to be able to identify it easily, such a turbine engine is referred to as a “compact turbine engine”.
In order to improve the performance of a compact turbine engine, and in particular its fuel consumption, the power plant may include a heat exchanger. Although the turbine engine is indeed compact, the heat exchanger is found on the contrary to be bulky. By way of example, the heat exchanger serves to preheat the air between the outlet from a compression stage of the turbine engine and a combustion chamber of the turbine engine, by using hot gas taken from the outlet of the turbine engine.
The heat exchanger is then fastened to the turbine engine in order to heat the fresh air as compressed by the gas generator prior to entering the combustion chamber.
Thus, fresh air is sucked into the turbine engine and is then compressed by each compression stage. The compressed fresh air is directed into the heat exchanger in order to be heated prior to reaching the combustion chamber. Under such circumstances, the compressed air is burnt together with fuel so as to generate hot gas that expands through at least one turbine. The turbine engine can thus comprise a turbine that is connected to the compressor stages and a free working turbine, which turbines are rotated by said hot gas. The hot gas is then collected by the heat exchanger in order to heat the fresh air sucked in by the turbine engine prior to releasing the hot gas into the atmosphere.
The assembly comprising a compact turbine engine and a heat exchanger is then found to be bulky compared with a conventional engine, but in contrast, it may present limited fuel consumption.
Nevertheless, arranging such an assembly is not at all obvious.
Putting the heat exchanger into place can lead to an increase in the width and/or the height and/or the length of the covers of the aircraft. The total surface area of the aircraft, and in particular its frontal surface area, is then increased compared with a conventional installation. This can lead to an increase in the aerodynamic drag of the aircraft.
Arranging a compact turbine engine coupled with a heat exchanger can also lead to a significant change in the position of the center of gravity of the aircraft, and that can have harmful impacts on the fin of the aircraft, for example. In particular, the vertical and horizontal stabilizers may then need to be dimensioned accordingly in order to guarantee static stability of the aircraft.
Document EP 1 216 190 describes an integrated engine and main gearbox.
A turbine engine is mounted in a housing, an main gearbox is incorporated in the housing and connected to the turbine. The main gearbox is mounted in a casing, with the casing and the housing being integrated with each other to constitute a single unit.
The turbine engine has a horizontal outlet shaft for driving the main gearbox.
Document FR 2 956 700 describes a turbine engine with an outlet shaft that extends substantially vertically under normal conditions of use, which shaft is held by a single bearing.
Document U.S. Pat. No. 5,226,350 describes an aircraft having a ring surrounding two contrarotating rotors. An engine is arranged within the ring in order to drive rotation of a hub carrying the contrarotating rotors. The engine is connected to the hub by a long shaft that tolerates axial, angular, and/or parallel misalignments between the hub and the engine.
Document U.S. Pat. No. 5,108,043 describes a helicopter power plant having two engines. Each engine drives a main gearbox via a transmission shaft having fluting at one end and carrying a gearwheel at its other end.
Document EP 0 760 777 describes a main gearbox having a planetary (epicyclic) gear train. An engine may also be connected to the main gearbox via bevel means.
Document DE 200 06 526 describes a shaft driving a rotor by means of a belt.
Those documents therefore do not provide teaching relating to arranging a power plant comprising a main gearbox that is driven in rotation by a compact turbine engine in co-operation with a heat exchanger.
Also known are the following documents: US 2005/115770 A1, U.S. Pat. No. 5,823,470 A, U.S. Pat. No. 5,054,716 A, GB 940 024 A, US 2011/121127 A1, and FR 2 905 983 A1.
Document US 2005/115770 A1 proposes an installation having a tilting gearbox.
Document U.S. Pat. No. 5,823,470 A describes an aircraft having two tilting rotors.
Document U.S. Pat. No. 5,054,716 A also describes a convertible aircraft having a turbine engine meshing with a main gearbox having a mast.